Sleep is one of the greatest scientific enigmas; what is does for the brain, individual neurons or glia is not defined on any level. It is unlikely that we will ever understand how the brain works until our understanding of the molecular regulation of sleep improves. Most people subjectively recognize that sleep increases after sleep deprivation or during the course of infectious disease. there is a rapidly growing body of evidence implicating cytokines in these responses and in the regulation of physiological sleep. We hypothesize that tumor necrosis factor alpha (TNFalpha) is one of the key substances involved in the regulation of sleep and in the sleep responses to infection and sleep deprivation. Data supporting this hypothesis are: 1) TNFalpha enhances non-rapid-eye movement sleep (NREMS) in rabbits; 2) anti-TNFalpha reduces NREMS in rats; 3) peptide fragments of TNFalpha containing a region known to interact with the TNF receptor also enhance NREMS; 4) TNF production by systemic cells increases during sleep deprivation and 5) TNFalpha- containing neurons are found in normal brain; 6) in humans plasma levels of TNFalpha vary directly with the power of EEG slow waves. The hypothesis will be tested by: 1) expansion of preliminary data to determine the effects of TNFalpha over a 24 hr period and at different times of the day in rats and rabbits; 2) the second specific aim will determine what role TNFalpha plays in normal sleep, sleep recovery after sleep deprivation and sleep responses to bacterial products. In each case, responses will be compared before and after rats and rabbits are treated with either anti-TNFalpha antibody or the soluble TNF receptor. It is anticipated that these latter substances will block sleep responses to sleep deprivation and bacterial products and also inhibit normal sleep; 3) finally, the levels of TNFalpha and TNF mRNA in brain will be determined at various times of the day and before and after sleep deprivation and administration of bacterial products. TNFalpha levels will be measured by bioassay and TNFalpha mRNA by Northern blot analyses. It is anticipated that the proposed experiments will: 1) verify a role for TNF in sleep regulation; 2) provide a molecular mechanistic approach to sleep regulation; 3) identify one of the endogenous substances involved in sleep responses to sleep deprivation and infection and 4) aid in our understanding of cytokine regulation in brain.